RF ID tag reader utilizing a scanning antenna system and method

ABSTRACT

An RF ID tag system and method that utilizes an RF ID tag and an RF ID tag reader which incorporates a dynamically reconfigurable wireless antenna and/or an array antenna and/or a switched polarization antenna. The dynamically reconfigurable wireless antenna embodiment comprises at least one multi-layered RF module, said at least one RF module further comprising at least one RF connector for receipt of at least one RF signal and at least one layer of tunable dielectric material and one layer of metal fabricated into said RF module; an RF motherboard for acceptance of RF signals and distribution of the transmit energy to said RF module at the appropriate phases to generate a beam in the commanded direction and width; and a controller for determining the correct voltage signal to send to said at least one multi-layered RF module.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application is a continuation in part of patent applicationSer. No. 10/388,788, entitled, “WIRELESS LOCAL AREA NETWORK AND ANTENNAUSED THEREIN” “filed Mar. 14, 2003, by Hersey et al., which claimed thebenefit of priority under 35 U.S.C Section 119 from U.S. ProvisionalApplication Ser. No. 60/365,383, filed Mar. 18, 2002.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] This invention relates generally to position determination andtracking systems. More specifically, this invention relates to radiofrequency identification (RFID) tag systems, methods and readers. Stillmore specifically, the present invention relates to RFID tags and tagreaders that utilize a scanning antenna or an electronically steerablepassive array antenna for significant system improvements.

[0004] 2. Background Art

[0005] Many product-related and service-related industries entail theuse and/or sale of large numbers of useful items. In such industries, itmay be advantageous to have the ability to monitor the items that arelocated within a particular range. For example, within a particularstore, it may be desirable to determine the presence and position ofinventory items located on the shelf, and that are otherwise located inthe store.

[0006] A device known as an RFID “tag” may be affixed to each item thatis to be monitored. The presence of a tag, and therefore the presence ofthe item to which the tag is affixed, may be checked and monitored bydevices known as “readers.” A reader may monitor the existence andlocation of the items having tags affixed thereto through one or morewired or wireless interrogations. Typically, each tag has a uniqueidentification number that the reader uses to identify the particulartag and item.

[0007] Currently, available tags and readers have many disadvantages.For instance, currently available tags are relatively expensive. Becauselarge numbers of items may need to be monitored, many tags may berequired to track the items. Hence, the cost of each individual tagneeds to be minimized. Furthermore, currently available tags consumelarge amounts of power. These inefficient power schemes also lead toreduced ranges over which readers may communicate with tags in awireless fashion. Still further, currently available readers and tagsuse inefficient interrogation protocols. These inefficient protocolsslow the rate at which a large number of tags may be interrogated.

[0008] As the antennas in readers are typically omni-directional or, atbest, manually directed, positioning information can only be obtained ifthe tags can be sure of their position and can relay the information tothe reader. However, if the tags are moved or are moving or do notpossess their position information, their angular position cannot bedetermined. Thus, there is a strong need in the art for an RF ID tagsystem and method that can determine the angular position of the tagrelative to the reader.

[0009] Further, because the antennas are omni-directional and areconstrained by FCC power limitations and other power constraints asmentioned above, the range is very severely limited. Hence, there is astrong need in the industry to provide an antenna that can allow forscanning and directionality for significant signal gain and overcomingmultipath problems. Since omni-directional antennas always read all tagsat all times, this limits the number of tags a reader can handle. With adirectional beam, you can have more total tags in the area since onlythe tags that are being illuminated by the beam will be read.

[0010] Thus, in summary, what is needed is a tag that is inexpensive,small, and has reduced power requirements, can provide tag directionalinformation and that can operate across longer ranges, so that greaternumbers of tags may be interrogated at faster rates and with positioninformation.

SUMMARY OF THE INVENTION

[0011] The present invention includes an RF ID tag system and methodincluding an RF ID tag and RF ID tag reader that utilizes a dynamicallyreconfigurable wireless antenna that comprises at least one RF module(which can be multilayered), said at least one RF module furthercomprising at least one RF connector for receipt of at least one RFsignal and at least one layer of tunable dielectric material and onelayer of metal fabricated into said RF module; an RF motherboard foracceptance of RF signals and distribution of the transmit energy to saidRF module at the appropriate phases to generate a beam in the commandeddirection and width; and a controller for determining the correct signal(for example, but not limited to, voltage signal) to send to said atleast one RF module. The scanning antenna operation is in any one, allor part of the following frequencies: the 2.4 GHz band; the 5.1 to 5.8GHz band; the 860-960 MHz band; or the 433 MHz band.

[0012] The invention also encompasses a method of tracking an object,person or thing, said method comprising the steps of associating an RFID tag with said object, person or thing; providing an RF ID tag readerwith a scanning antenna for transmitting information to, and receivinginformation from, said RF ID tag, said RF ID tag may contain informationabout said object, person or thing; wherein said scanning antennacomprises at least one multi-layered RF module, said at least one RFmodule further comprising at least one RF connection for receipt of atleast one RF signal and at least one tunable or switchable device; an RFmotherboard for acceptance of RF signals and distribution of thetransmit energy to said RF module at the appropriate phases to generatea beam in the commanded direction and width; and a controller fordetermining the correct voltage signal to send to said at least onemulti-layered RF module.

[0013] Further, this invention discloses and claims an RF tag readerwherein said reader comprises a microcontroller associated with atransceiver; a scanning antenna interfaced with said microcontroller andtransceiver, said antenna comprising at least one multi-layered RFmodule, said at least one RF module further comprising at least one RFconnector for receipt of at least one RF signal and at least one layerof tunable dielectric material and one layer of metal; an RF motherboardfor acceptance of RF signals and distribution of the transmit energy tosaid RF module at the appropriate phases to generate a beam in thecommanded direction and width; and a controller for determining thecorrect voltage signal to send to said at least one multi-layered RFmodule.

[0014] In a further embodiment the present invention discloses andclaims an RF ID card reader wherein said card reader comprises RF IDcircuitry to generate an RF ID signal; a transceiver in communicationwith said RF ID circuitry; and an array antenna associated with saidtransceiver for scanning an area for at least one tag and establishingcommunication with at least one tag and wherein said array antennafurther comprises a radiating antenna element; at least one parasiticantenna element; at least one voltage-tunable capacitor connected tosaid at least one parasitic antenna element; and a controller forapplying a voltage to each voltage-tunable capacitor to change thecapacitance of each voltage-tunable capacitor and thus control thedirections of maximum radiation beams and minimum radiation beams of aradio signal emitted from said radiating antenna element and said atleast one parasitic antenna element.

[0015] Disclosed also herein is a position determination system, whereinat least one RF ID tag is associated with an object, person or thing andat least one RF ID tag reader establishes communication with said atleast one RF ID tag. The at least one RF ID tag reader includes at leasttwo electronically steerable scanning antennas and determines therelative location of said at least one RF ID tag by triangulating theangular information between said at least one RF ID tag and said atleast two electronically steerable scanning antennas which areassociated with said at least one RF ID tag reader.

[0016] The method of position determination is accomplished byassociating at least one RF ID tag with anything from which positioninformation or tracking information is desired from, such as any object,person or thing. Then communication is established between at least oneRF ID tag reader and said at least one RF ID tag. In a first embodiment,at least one RF ID tag reader includes at least two electronicallysteerable scanning antennas. At this point one can determine thelocation of said at least one RF ID tag relative to said at least one RFID tag reader by triangulating the angular information between said atleast one RF ID tag and said at least two electronically steerablescanning antennas associated with said at least one RF ID tag reader.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The present invention is described with reference to theaccompanying drawings. In the drawings, like reference numbers indicateidentical or functionally similar elements. Additionally, the left-mostdigit(s) of a reference number identifies the drawing in which thereference number first appears.

[0018]FIG. 1a is a block diagram of the basic sections of an RF ID tag.

[0019]FIG. 1b is a block diagram of the basic sections of an RF ID tagreader.

[0020]FIG. 1c is a depiction of the method of tracking an object,further depicting the directionality capability and the scanningcapability of the scanning antenna of the present invention as well amultipath environment which is improved by the directional ability ofthe present invention.

[0021]FIG. 1d is an illustration of an example RF ID tag environmentwith a single carrier version of the present invention;

[0022]FIG. 2 is an illustration of an example RF ID tag environment withthe multi-beam embodiment of the present invention;

[0023]FIG. 3 is an illustration of an example RF ID environment with themultiple beams, frequency reuse embodiment of the present invention;

[0024]FIG. 4 depicts the RF ID tag reader antenna of the presentinvention;

[0025]FIG. 5 is an exploded view of the RF ID tag antenna of the presentinvention;

[0026]FIG. 6 is a more detailed exploded view of the RF Boardsconstruction of the RFID tag antenna of the present invention;

[0027]FIG. 7 is a more detailed exploded view of the base constructionof the RF ID tag antenna of the present invention;

[0028]FIG. 8 is a more detailed exploded view of the RF Moduleconstruction of the RF ID tag reader antenna of the present invention;

[0029]FIG. 9 is a depiction of a detailed view of the various inputsinto the base of the RF ID tag reader antenna of the present invention.

[0030]FIG. 10 is a block diagram of the basic sections of an RF ID tagreader with the electronically steerable passive array antennaincorporated therein.

[0031]FIG. 11 is a block diagram of a wireless communications networkcapable of incorporating an array antenna in an RF ID tag system of thepresent invention;

[0032]FIG. 12 is a perspective view that illustrates the basiccomponents of a first embodiment of the array antenna shown in FIG. 11;

[0033]FIG. 13 is a side view of a RF feed antenna element located in thearray antenna shown in FIG. 12;

[0034]FIG. 14 is a side view of a parasitic antenna element and avoltage-tunable capacitor located in the array antenna shown in FIG. 12;

[0035]FIGS. 15A and 15B respectively show a top view and across-sectional side view of the voltage-tunable capacitor shown in FIG.14;

[0036]FIGS. 16A and 16B respectively show simulation patterns in ahorizontal plane and in a vertical plane that were obtained to indicatethe performance of an exemplary array antenna configured like the arrayantenna shown in FIG. 12 and used in the RF ID tag system of the presentinvention;

[0037]FIG. 17 is a perspective view that illustrates the basiccomponents of a second embodiment of the array antenna shown in FIG. 11;

[0038]FIG. 18 is a perspective view that illustrates the basiccomponents of a third embodiment of the array antenna shown in FIG. 11;and

[0039]FIG. 19 is a block diagram of the switched polarization antennathat can be used in the RF ID tag system of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0040] The present invention serves as an internal or external antennafor a RF ID TAG reader application as well as a position determinationand tracking system and method. The antenna interfaces with an RFIDreader that can be used in a RF ID tag system for significantperformance advantages. The antennas described herein can operate in anyone, all or part of the following frequencies: the 2.4 GHz GHzIndustrial, Scientific and Medical (ISM) band; the 5.1 to 5.8 GHz band;the 860-960 MHz band; or the 433 MHz band; although it is understoodthat they can operate in other bands as well. A software driverfunctions to control the antenna azimuth scan angle to maximize thereceived wireless signal from a tag associated with a reader. In a firstembodiment, the key performance requirement to steer a beam with 6 dBiof gain throughout a 360° azimuth, or any segmentation of 360 degrees,scan is enabled

[0041] Existing RF ID TAG READERS currently use fixed antennas. Mostoften, omni-directional antennas are used, which are typicallyintegrated into the RF ID TAG READER card or exist as an integralmonopole antenna. External high gain antennas exist; however, these havea fixed beam that the user must manipulate by hand. The presentinvention requires no user intervention and ensures maximum performance.

[0042] The basic components of the present invention include a RF ID tagand an RF ID reader, with the scanning antenna of the present inventionassociated with the reader and functioning in several differentembodiments as described below.

[0043] Referring now the figures, FIG. 1a shows a block diagram of atypical RF ID tag or transponder circuit. Such RF ID tag systems arecommercially available from Disys Inc. in Toronto, Canada as their 90Series RF ID tags and from Hughes ID Corporation in Mission Viejo,Calif. Dysis publishes a “90 Series RF/ID System Applications Manual forCRM-90 Readers and 90 Series Tags, the details of which are herebyincorporated by reference. RF ID tag reader/writer circuits suitable foruse as interface with the scanning antenna are also commerciallyavailable from these two sources. RF ID tags are also currentlycommercially available from Atmel Corporation of Colorado Springs, Colo.and Eurosil, a Division of Daimler Benz located in Munich. Reader/writersystems are also available from Indala, a division of Motorola locatedin San Jose, and as two integrated circuit sets (one transceiver and onedigital section) are commercially available from another division ofDaimler Benz called AEG Telefunken. The details of these commerciallyavailable RF ID tags and RF ID tag readers are hereby incorporated byreference. A block diagram of a typical circuit that may be used for theRF ID tag reader 10 b is shown in FIG. 1b.

[0044] An RF ID tag, 10 a shown in FIG. 1a, is a small circuit whichincludes a radio transceiver 15 a which is powered by power derived fromrectification of incoming RF signals, the process of deriving suitablepower from the incoming RF being performed by power supply section 35 a.The RF ID tag also has on-board nonvolatile memory 20 a for storing datasuch as an identifier code which identifies the type of person, objectof things that the tag is attached to and a serial number identifyingthe particular tag. The memory is nonvolatile and may be both writtenand read by RF communication to the chip in the preferred embodiment,but in alternative embodiments, the memory may be fixed and unalterablesuch as ROM or even hardwired connections. Typically, the nonvolatilememory is of the ROM, EEPROM or anti-fuse variety. Several U.S. patentsnaming inventor Bruce Rosener and assigned to Unisys Corporation andInstant Circuit exist describing the structure of nonvolatile antifuzememory in an RF ID tag with no independent power source. These patentsare: U.S. Pat. Nos. 4,442,507; 5,296,722; 5,407,851; 4,796,074; and5,095,362. Further, recent advancements in RF Tag technology aredescribed in U.S. Pat. No. 5,550,547 entitled, “Multiple item radiofrequency tag identification protocol”; U.S. Pat. No. 5,995,006entitled, “Radio Frequency Tag”; and U.S. Pat. No. 5,883,575 entitled,“RF-tags utilizing thin film bulk wave acoustic resonators”. The detailsof these patents are hereby incorporated by reference and it isunderstood that future advancements in RF ID tag technology can beutilized in the novel scanning antenna feature in the reader of thepresent invention.

[0045] The RF ID tag also includes digital control circuitry 30 a whichcontrols switching of the antenna connection, whether the tag is sendingor receiving, and reading and writing the memory section. Typicalinstruction sets for the more sophisticated RF ID tags currentlyavailable include commands to Read Word n, Write Word n, Read Delayedand Turn Off such that the RF ID tag does not respond to interrogations.

[0046] The function of the RF ID tag is to receive an excitation signalfrom the reader, modify it in some way which is indicative of dataidentifying the particular tag that did the modification, therebyidentifying the particular item to which the tag is attached, and thentransmitting back to the reader. In the absence of stimulus from thereader, the tag is dormant and will not transmit data of its ownvolition.

[0047] Typically, the low frequency RF ID tags are very small and areaffixed to a substrate upon which a coiled conductive trace serving asan antenna is formed by integrated circuit or printed circuittechnology. The digital control circuitry also keeps the tag “locked” sothat it cannot alter data in the memory or read and transmit data fromthe memory until the digital circuitry detects reception of the unlocksequence. The RF ID reader/writer unit knows the unlock sequence for theRF ID tags to be unlocked for interrogation or writing data thereto, andtransmits that sequence plus interrogation or other commands to the RFID tags.

[0048] FIG 1 b illustrates a first embodiment of the reader as used inthe present invention. However, it is understood that the novel scanningantenna can be used with any reader that can benefit from the use of ascanning antenna as described below. FIG. 1b depicts a block diagram ofa typical RF ID tag reader 10 b from the class of devices that can beused as the RF ID tag reader 10 b of the present invention (hereafterreferred to as the reader). The reader 10 b has a range of from a fewmillimeters to several meters and more depending upon size of the RF IDtag (hereafter may also be referred to as a transponder), thedirectionality of the beam of the scanning antenna, the operatingfrequency, and whether the transponder is a passive or active type. Thereader 10 b can contain a microcontroller 20 b for controlling readerfunctionality and programming and is connected to a scanning antenna 400via interface 15 b. A transceiver 25 b can be associated with saidmicrocontroller for generation and reception of RF signals to be passedto scanning antenna 400 via interface 15 b

[0049] Power is provided by power supply 40 b and a serial input/out 35b is provided to provide information to microcontroller 20 b via serialcommunications link 30 b. This enables external programming andfunctionality control of microcontroller 20 b.

[0050] Transponders of a passive variety are those discussed above whichgenerate power to operate the circuits therein from an excitation signaltransmitted from the reader. There is another class of transponderhowever of an active class which some form of energy source independentof the reader such as a small primary cell such as a lithium battery.

[0051]FIG. 1c is a depiction of the method of tracking an object andfurther depicting the directionality capability and the scanningcapability of the scanning antenna 400 of the present invention; as wella multipath environment which is improved by the directional ability ofthe present invention. A warehouse 5 c is represented in FIG. 1c with anRF ID tag system implemented therein. Crates 12 c, 14 c, 16 c, 18 c, 20c, 22 c, 24 c, 26 c, 28 c, 30 c, 32 c and 34 c are shown as typicalcrates might be stored in a typical warehouse 5 c. In a typical metalwarehouse, a great amount of multipath is created while communicatingwith the tags associated with a large plurality of items to be tracked.In this case, tags 10 c, 15 c, 20 c, 30 c, 35 c, 40 c, 45 c, 50 c, 55 c,60 c, 65 c and 70 c are associated with crates 12 c, 14 c, 16 c, 18 c,20 c, 22 c, 24 c, 26 c, 28 c, 30 c, 32 c and 34 c respectively. Becausescanning antenna 400 is associated with reader 10 b, the reader can scannarrow beam widths for tag transmissions and can transmit to the tags innarrow beam widths. This greatly diminishes the effects of multipath,improves range, decreases power requirements, improves data rate andoverall provides for a much improved RF ID tag tracking system. Themethod used in this embodiment includes the steps of associating an RFID tag with said object, person or thing (a crate in the embodiment ofFIG. 1c); providing an RF ID tag reader 10 b with a scanning antenna 400for transmitting information to, and receiving information from, said RFID tag(s) 10 c, 15 c, 20 c, 30 c, 35 c, 40 c, 45 c, 50 c, 55 c, 60 c, 65c and 70 c, said RF ID tag containing information about crates 12 c, 14c, 16 c, 18 c, 20 c, 22 c, 24 c, 26 c 28 c, 30 c, 32 c and 34 c; whereinsaid scanning antenna comprises at least one RF module (which can bemulti-layered), said at least one RF module further comprising at leastone RF connection for receipt of at least one RF signal and at least onetunable or switchable device; an RF motherboard for acceptance of RFsignals and distribution of the transmit energy to said RF module at theappropriate phases to generate a beam in the commanded direction andwidth; and a controller for determining the correct voltage signal tosend to said at least one multi-layered RF module. Further, and asdescribed in more detail below, the aforementioned RF ID tag system canbe implemented wherein said antenna is an array antenna, and whereinsaid array antenna comprises a radiating antenna element; at least oneparasitic antenna element; at least one voltage-tunable capacitorconnected to said at least one parasitic antenna element; and acontroller for applying a voltage to each voltage-tunable capacitor tochange the capacitance of each voltage-tunable capacitor and thuscontrol the directions of maximum radiation beams and minimum radiationbeams of a radio signal emitted from said radiating antenna element andsaid at least one parasitic antenna element.

[0052] The present invention can be implemented in several networkingembodiments which benefit from the scanning antenna 400 incorporatedherein. FIG. 1d depicts a single carrier version wherein network 100 hasreader 125 and tags 105, 120, 135 and 145; such as a tag associated withanything for which tracking information is desired. In FIG. 1d this isdepicted as 110 and is understood that it can be anything from palletsin a warehouse to people in an amusement park. In this single carriersolution, multiple channels are possible using the tunable technology ofthe present invention. In this example, the multiple channels 115 and130 allow for communication with many tags and, if desired communicationat high data rates with the tags of at least 11 Mbps bandwidth usingonly 22 MHz of spectrum and in a narrow transmission beam for greaterrange or data throughput and less multipath interference.

[0053]FIG. 2 depicts the multi-beam embodiment wherein RF ID tag system200 has RF ID tag reader 240 and tags 205-235 which can be associatedwith items to be tracked 245. In this multi-carrier solution multiplebeams 250 and 255 are used with one beam for each channel. In thisembodiment, at least 22 Mbps is achieved with 44 MHz of spectrum, whichenables tracking and position determination of many tags.

[0054]FIG. 3 depicts the multiple beams, frequency reuse embodiment ofthe present invention. Herein RF ID tag system 300 has RF ID tag reader360 and tags 305-335 for tracking and position determination. In thismultiple-beam, frequency reuse embodiment individual channels 350 and355 for all beams are used. An item to be tracked associated with tag305 is illustrated at 365. It is understood that all tags will have areception antenna and in this embodiment at least 22 Mbps using 22 Mhzis achieved and a large number of tags can be tracked and positioneddetermined. Tags are well known in this art and it is understood thatmany different type of tags can be used with the present inventionincluding the tag described above in FIG. 1a.

[0055] As will be shown in the figures to follow, the scanning antennaused with the reader 10 b of the preferred embodiment of the presentinvention may contain the following subassemblies in antenna 400, withexploded view shown as 500: RF Modules 515, RF Motherboard 545,controller connector 915 (with connector screws 910 and 920), base 410,radome 405, external RF cables [MMCX to transceiver card] (not shown),external control cables (not shown), external power supply connector 905and a software driver. The external RF and control cables connect theantenna 400 to the RF ID tag reader 10 b via interface 15 b.

[0056] The power supply cable connects between an AC outlet and theantenna 400; although, it is understood that any power supply can beutilized in the present invention. Further, power can be supplied byreader 10 b, through interface 15 b and by power supply 40 b. MatingMMCX jacks (or any similar RF connectors now known or later developed)415 and 420, DB-25 female, and DC power jack connectors 905 are locatedon the side of the base 410 and can facilitate connection with interface15 b. The DC power jack 905 and DB-25 connector 915 are right angleconnectors integral to the controller Printed Circuit Board (PCB), withthe mating portions 415, 420 exposed through the base 410, again tofacilitate interconnection with interface 15 b. Once inside the housing,the RF signals are transferred to the RF motherboard 545 via flexiblecoaxial cables (not shown) to a surface mount interface 535.

[0057] The controller determines the correct voltage signals to send tothe motherboard 545, as requested by the received software command andthe current internal temperature sensed at the phase shift modules.These voltages are sent across a ribbon cable (not shown) to theswitches and phase shifters located on the motherboard 545. Thecontroller also provides feedback to the reader circuitry via interface15 b so that the software can determine if the antenna is present ornot. The controller mounts rigidly to the inside bottom of the base 410with its main connector 915 exposed.

[0058] The motherboard distributes the RF signals to the nine RF modules515 via RF connectors 510 and 520. The dual RF input allows for eithersingle or dual polarization which can be either linear or circular.Simply horizontal or vertical polarization is also enabled. The signalfrom the main connectors 595 and 535 are divided three ways, each to aphase shifter and then an SP3T switch. The outputs of the switchterminate in nine places, one for each RF module. This permits any ofthree consecutive RF modules 515 to be active and properly phased at anytime. The motherboard (not shown) mounts rigidly to the top side of thebase 410, which is stiffened to ensure that the phase shift and powerdivider modules will not shatter under expected environmentalconditions. Cutouts 575 exist in the top of the base for connector pinsand cable access features.

[0059] The RF modules consist of a multilayer antenna for broadbandwidth. They are connected to the motherboard via a flex microstripcircuit. The modules are mounted perpendicular to the motherboard, andare secured to the base via vertical triangular posts 525.

[0060] The radome 405 fits over the product and is fused to the base410, both at the bottom of the radome 405 and top of the base 410intersection, and at the base posts to the inside top of the radome 405.

[0061] Subassembly Descriptions

[0062] RF Modules 515

[0063] In the preferred embodiment of the present invention, nine RFmodules 515 are required for the assembly of each antenna. As shown inFIG. 8, 800, each module is a multilayer bonded structure consisting ofalternating metal 805, 815, 825 and dielectric 810, 820 layers.Although, nine RF modules 515 are depicted in this preferred embodiment,it is understood that one skilled in the art can vary the number of RFmodules according to performance parameters and design choice—such asthe number of tags to be tracked and the distance anticipated from thereader to the tags.

[0064] The outer layer 825 of the subassembly 515 can be a stamped brasselement about 1.4″±0.002″ square. This brass element is bonded to ablock of dielectric 1.5″±0.01″ square 820. A target material can bepolystyrene if cost is a consideration, where the requirements are adielectric constant between 2.6 and 3.0. Once established in the design,the dielectric constant should be maintained at frequency within 2%. Theloss tangent of this dielectric should not exceed 0.002 at 2.5 GHz. Theabove assembly is bonded to an inner metal layer of stamped copperelement 815 plated with immersion nickel-gold and is about 1.4″±0.002″square. The above assembly is then bonded to another block of identicaldielectric 1.7″×1.8″±0.01″ square 805. This subassembly is completedwith a bonded flex circuit described below in the interconnectionsection.

[0065] RF Motherboard 545

[0066] The RF motherboard 545 consists of a 9-sided shaped microwave4-layer PCB. Although it is understood that the shape of the motherboardand the number of sides can be modified to alternate shapes and sideswithout falling outside the scope of the present invention. In thepresent invention, the inscribed circular dimension is 4.800±0.005″.Rogers RO4003 material with ½ ounce copper plating is used for each ofthe three 0.020″ dielectric layers. This stack up permits a microstriptop layer and an internal stripline layer. All copper traces can beprotected with immersion nickel-gold plating. Alternate substratematerials can be considered for cost reduction, but should have adielectric constant between 2.2 and 3.5, and a loss tangent notexceeding 0.003 at 2.5 GHz.

[0067] The motherboard functions to accept two signals from the MMCXconnectors 415, 420 (although MMCX connectors are used, it is understoodthan any similar RF connectors now known or later developed can also beused) from individual coaxial cables and properly distribute thetransmit energy to the appropriate elements at the appropriate phases togenerate a beam in the commanded direction. The coaxial cables have asnap-on surface mount connection to the motherboard. Each of thesecables feed a 3-way power divider module, described below. The output ofeach power divider connects to a 90°-phase shifter module, alsodescribed below. The output of each phase shifter feeds a SP3T switch.In the preferred embodiment, a Hittite HMC241QS16 SP4T MMIC switch wasselected, although a multitude of other switches can be utilized. Threeof the switched outputs connect go to the module connection landings, inalternating threes; that is, switch #1 connects to modules 1, 4, and 7,etc. It is the alternating nature that requires the motherboard to bemultilayer, to permit crossover connections in the stripline layer.Thus, one skilled in the art can utilize design choice regarding thenumber of layers and switch to module connections. At the output of eachswitched line is a 10 V DC blocking capacitor; and, at each end of thephase shifter is a 100 V DC blocking capacitor. These fixed capacitorsshould have a minimum Q of 200 at frequency, and are nominally 100 pF.

[0068] Three-Way Divider

[0069] The three-way divider can be a 1″×1″×0.020″ 96% Alumina SMD part.Copper traces are on the top side and a mostly solid copper ground planeis on the bottom side, except for a few relief features at the portinterfaces. All copper is protected with immersion nickel-gold plating.There are no internal vias on this preferred embodiment of the presentinvention. Provisions can be made to enable the SMD nature of thisinherently microstrip four-port device.

[0070] 90° Phase Shifter

[0071] The 90° phase shifter is a 1″×1″×0.020″ 96% Alumina SMD part.Copper traces are on the top side and a mostly solid copper ground planeis on the bottom side, except for a few relief features at the portinterfaces. All copper is protected with immersion nickel-gold plating.There are two internal vias to ground on the device. Two thin film SMDParascan varactors are SMT mounted to the top side of this device. Someprovisions can be made to enable the SMD nature of this inherentlymicrostrip two-port device. Parascan is a trademarked tunable dielectricmaterial developed by Paratek Microwave, Inc., the assignee of thepresent invention. Tunable dielectric materials are the materials whosepermittivity (more commonly called dielectric constant) can be varied byvarying the strength of an electric field to which the materials aresubjected or immersed. Examples of such materials can be found in U.S.Pat. Nos. 5,312,790, 5,427,988, 5,486,491, 5,693,429 and 6,514,895.These materials show low dielectric loss and high tunability. Tunabilityis defined as the fractional change in the dielectric constant withapplied voltage. The patents above are incorporated into the presentapplication by reference in their entirety.

[0072] Controller

[0073] The controller consists of a 3″×5″×0.031″ 4-layer FR-4 PCB. Ithas SMD parts on the top side only, as is mounted to the bottom of thebase 410. The controller has two right angle PCB-mount externalconnectors 415, 420 that can be accessed through the base 410. A DB-25female connector 915 is used for the command and a DC power jack 905 isused to receive the DC power. It is, of course, understood that anyconnector can be used for command and power connection.

[0074] The controller contains a microprocessor and memory to receivecommands and act on them. Based upon the command, the controller sendsthe proper TTL signals to the SP3T switches and the proper 10 to 50 V(6-bit resolution) signals to the phase shifters. To send these highvoltage signals, a high voltage supply, regulator, and high voltagesemiconductor signal distribution methods are used.

[0075] Base 410

[0076] The design choice for this preferred embodiment has a base formedfrom black Acrylonitrile Butadiene Styrene (ABS) and measures 6.5″ roundin diameter and 0.5″ in main height. The bottom is solid to accommodatethe controller board, and the side has one flat surface for theconnectors. The top side at the 0.5″ height is reinforced in thicknessto achieve the rigidity to protect the Alumina modules; or, a thin 0.1″aluminum sheet could be used in addition at the top if needed.

[0077] Extending from the main top side level are nine verticaltriangular posts 525 that make the overall height 3.0 inches, minus thethickness of the radome 405. This ensures that the radome 405 insidesurface contacts the base posts. These posts 525 provide alignment andcentering for the RF modules that connect to the RF motherboard via flexcircuit sections. The RF modules are bonded in place to these posts. Atthe lower portion of base 410 are openings 555 and 590, whereat RFconnectors 420 and 415 protrude.

[0078] Internal Interconnect and Distribution

[0079] The RF MMCX bulkhead jacks 415, 420 are connected to the RFmotherboard 545 via thin coaxial cables. These cables are integral tothe bulkhead connector 595 and 535 and have surface mount compatiblesnap-on features to attach to the motherboard. The controller sends itsvoltage signals to the RF motherboard 545 via a ribbon cable. Matingpins are provided on the controller and motherboard to accept the ribboncable connectors.

[0080] The RF modules 515 are connected to the motherboard using a flexcircuit. This flex circuit is made of 0.015″ thick Kapton and has amatching footprint of the lower dielectric spacer (1.7″×1.8″) and has anadditional 0.375″ extension that hangs off the 1.7″ wide edge. The sideof the circuit bonded at the dielectric spacer is completely copperexcept for a cross-shaped aperture, centered on the spacer. The exteriorside of the circuit has two microstrip lines that cross the aperture andproceed down to the extension, plus the copper extends past the Kaptonto allow a ribbon-type connection to the motherboards 545. At the bottomof the spacers 560 and throughout the extension there are coplanarground pads around these lines. These ground pads 570 are connected tothe reverse side ground through vias. These ground pads also extendslightly past the Kapton. Each module extension 530 can be laid on topof the motherboard and is soldered in place, both ground and main trace.All copper traces are protected by immersion nickel-gold plating.

[0081] End User Interconnect and Interfaces

[0082] The two coaxial cables carry the RF signals between the scanningantenna 400 and the reader 10 b via interface 15 b. One cable is used tocarry each linear polarization, horizontal and vertical, for diversity.Both cables have an MMCX plug on one end and a connector which mates tothe card on the other. This mating connector may be an MMCX, SMA, or aproprietary connector, depending upon the configuration of interface 15b.

[0083] The digital cable carries the command interface, and is astandard bi-directional IEEE-1284 parallel cable with male DB-25connectors, and made in identical lengths as the RF cable. The DC powersupply is a wall-mount transformer with integral cable that terminatesin a DC power plug. This cable plugs into the antenna's DC power jack.However, as mentioned above the power supply 1115 of reader 10 b canalso power scanning antenna 400 vi interface 15 b.

[0084] Radome Housing

[0085] A formed black ABS radome encloses the present invention andprotects the internal components. It is understood that this housing isbut one of any number of potential housings for the present invention.The outer diameter matches the base at 6.5″, and the height aligns tothe base vertical posts, for a part height of 2.5″. Thus the antenna is3.0″ in total height. The radome has a nominal wall thickness of 0.063″and a 1° draft angle. The top of the radome is nominally 0.125″ thick.

[0086] Fabrication

[0087] The controller can be screwed to the bottom of the base. Theinternal coaxial cable bulkheads are secured to the base. The copperribbon extensions of the RF modules are soldered in a flat orientationto the RF motherboard. The snap-on ends of the coaxial cables areattached to the motherboard/module assembly, which is lowered in placebetween the base vertical posts. The RF modules are secured to theposts, perpendicular to the motherboard. The radome is fused to the baseat its bottom and at the upper vertical posts.

[0088] For further elaboration of the fabrication of the presentinvention, FIGS. 4, 5, 6, 7 and 8 depict the present in invention withvarious levels of expansion. FIG. 4 depicts the scanning antenna 400 ofthe present invention in a completely fabricated view with the Radome405 placed on top of base 410 with RF connectors 415 and 420 protrudingfrom base 410.

[0089]FIG. 5 is an exploded view of the scanning antenna 400 of thepresent invention wherein all of the internal components of scanningantenna 400 can be seen. These include radome 405 and base 410 withrepresentative RF module 515 and RF connectors 510 and 520 locatedwithin said RF module 515. Expansion module 530 also has RF connectorsrepresented by 540. Posts for securing are depicted at 525 and spaces at560. As described above, RF motherboard is shown at 545 immediatelyabove base 410 and attached by screws 570. Main connectors 595 and 535are shown connected to RF motherboard 545 and expansion module 530. Alsoconnected to RF motherboard 545 is RF connector 550.

[0090] To more clearly depict the construction, FIG. 6 is a moredetailed exploded view of the RF Boards construction of the scanningantenna of the present invention showing the construction of expansionmodule 515 and RF motherboard 545. Further, FIG. 7 is a more detailedexploded view of the base 410 construction of the scanning antenna ofthe present invention.

[0091]FIG. 8 is a more detailed exploded view of the RF Moduleconstruction of the scanning antenna of the present invention. Thisincludes the placement of the dielectric material 810 and 820 adjacentto metal 805, 815 and 825. Although, the present depiction shows twodielectric layers and three metal layers, different layers can be usedbased on design choices and performance requirements.

[0092]FIG. 9 shows an actual representation of the invention hereindescribed with base 410 allowing for RF connectors 420 and 415 and DCconnector 905 and controller connector 915 with screws 910 and 920 forsecuring said controller connector.

[0093]FIG. 10 shows an alternate embodiment of the present inventionwhich utilizes an electronically steerable passive array antenna in lieuof the scanning antenna set forth above. The electronically steerablepassive array antenna is described in detail below and in a patentapplication filed by an inventor of the present invention on Aug. 14,2003, and is entitled, “ELECTRONICALLY STEERABLE PASSIVE ARRAY ANTENNA”,with attorney docket no. WJT08-0065, Ser. No. 10/413,317. FIG. 10depicts a block diagram of a typical RF ID tag reader 10 b as describedabove of the present invention. Again, the reader has a range of from afew millimeters to several meters and more depending upon size of the RFID tag, the directionality of the beam of the scanning antenna, theoperating frequency, and whether the transponder is a passive or activetype. The reader 10 b can contain a microcontroller 20 b for controllingreader functionality and programming and in this embodiment is connectedto an array antenna 90 b, via interface 15 b. As above, a transceiver 25b can be associated with said microcontroller 20 b for generation andreception of RF signals to be passed to array antenna 50 b via interface15 b

[0094] As above, power is provided by power supply 40 b and a serialinput/out 35 b is provided to provide information to microcontroller 20b via serial communications link 30 b. This enables external programmingand functionality control of microcontroller 20 b.

[0095] Referring to the drawings which incorporate the electronicallysteerable passive array antenna embodiment of the present invention,FIG. 11 is a block diagram of a wireless communications network 1100that can incorporate an array antenna 1102. Although the array antenna1102 is described below as being incorporated within a hub type wirelesscommunication network 1100 and within the RF ID tag system, it should beunderstood that many other types of networks can incorporate the arrayantenna 1102 to be incorporated into the RF ID tag system. For instance,the array antenna 1102 can be incorporated within a mesh type wirelesscommunication network, a 24-42 GHz point-to-point microwave network,24-42 GHz point-to-multipoint microwave network or a 2.1-2.7 GHzmultipoint distribution system. Accordingly, the array antenna 1102 ofthe present invention should not be construed in a limited manner.

[0096] Referring to FIG. 11, there is a block diagram of a hub typewireless communications network 1100 that utilizes the array antenna1102 of the present invention. The hub type wireless communicationsnetwork 1100 includes a hub node 1104 and one or more remote nodes 1106(four shown). The remote nodes 1106 of the present invention mayrepresent tags as described above.

[0097] The hub node 1104 incorporates the electronically steerablepassive array antenna 1102 that produces one or more steerable radiationbeams 1110 and 1112 which are used to establish communications linkswith particular remote nodes 1106 (such as tags). A network controller1114 directs the hub node 1104 and in particular the array antenna 1102to establish a communications link with a desired remote node 1106 byoutputting a steerable beam having a maximum radiation beam pointed inthe direction of the desired remote node 1106 and a minimum radiationbeam (null) pointed away from that remote node 1106. The networkcontroller 1114 may obtain its adaptive beam steering commands from avariety of sources like the combined use of an initial calibrationalgorithm and a wide beam which is used to detect new remote nodes 1106and moving remote nodes 1106. The wide beam enables all new or movedremote nodes 1106 to be updated in its algorithm. The algorithm then candetermine the positions of the remote nodes 1106 and calculate theappropriate DC voltage for each of the voltage-tunable capacitors 1206(described below) in the array antenna 1102.

[0098] A more detailed discussion about one way the network controller1114 can keep up-to-date with its current communication links isprovided in a co-owned U.S. patent application Ser. No. 09/620,776entitled “Dynamically Reconfigurable Wireless Networks (DRWiN) andMethods for Operating such Networks”. The contents of this patentapplication are incorporated by reference herein.

[0099] It should be appreciated that the hub node 1104 can also beconnected to a backbone communications system 1108 (e.g., Internet,private networks, public switched telephone network, wide area network).It should also be appreciated that the remote nodes 1106 can incorporatean electronically steerable passive array antenna 1102.

[0100] Referring to FIG. 12, there is a perspective view thatillustrates the basic components of a first embodiment of the arrayantenna 1102 a. The array antenna 1102 a includes a radiating antennaelement 1202 capable of transmitting and receiving radio signals and oneor more parasitic antenna elements 1204 that are incapable oftransmitting or receiving radio signals. Each parasitic antenna element1204 (six shown) is located a predetermined distance away from theradiating antenna element 1202. A voltage-tunable capacitor 1206 (sixshown) is connected to each parasitic antenna element 1204. A controller1208 is used to apply a predetermined DC voltage to each one of thevoltage-tunable capacitors 1206 in order to change the capacitance ofeach voltage-tunable capacitor 1206 and thus enable one to control thedirections of the maximum radiation beams and the minimum radiationbeams (nulls) of a radio signal emitted from the array antenna 1102. Thecontroller 1208 may be part of or interface with the network controller1114 (see FIG. 11).

[0101] In the particular embodiment shown in FIG. 12, the array antenna1102 a includes one radiating antenna element 1202 and six parasiticantenna elements 1204 all of which are configured as monopole elements.The antenna elements 1202 and 1204 are electrically insulated from agrounding plate 1210. The grounding plate 1210 has an area large enoughto accommodate all of the antenna elements 1202 and 1204. In thepreferred embodiment, each parasitic antenna element 1204 is arranged ona circumference of a predetermined circle around the radiating antennaelement 1202. For example, the radiating antenna element 1202 and theparasitic antenna elements 1204 can be separated from one another byabout 0.2λ0-0.5λ0 where λ0 is the working free space wavelength of theradio signal.

[0102] Referring to FIG. 13, there is a side view of the RF feed antennaelement 1202. In this embodiment, the feeding antenna element 1202comprises a cylindrical element that is electrically insulated from thegrounding plate 1210. The feeding antenna element 1202 typically has alength of 0.2λ0-0.3λ0 where λ0 is the working free space wavelength ofthe radio signal. As shown, a central conductor 1302 of a coaxial cable1304 that transmits a radio signal fed from a radio apparatus (notshown) is connected to one end of the radiating antenna element 1202.And, an outer conductor 1306 of the coaxial cable 1304 is connected tothe grounding plate 1210. The elements 1302, 1304 and 1306 collectivelyare referred to as an RF input 1308 (see FIG. 12). Thus, the radioapparatus (not shown) feeds a radio signal to the feeding antennaelement 1202 through the coaxial cable 1304, and then, the radio signalis radiated by the feeding antenna element 1202.

[0103] Referring to FIG. 14, there is a side view of one parasiticantenna element 1204 and one voltage-tunable capacitor 1206. In thisembodiment, each parasitic antenna element 1204 has a similar structurecomprising a cylindrical element that is electrically insulated from thegrounding plate 1210. The parasitic antenna elements 1204 typically havethe same length as the radiating antenna element 1202. Thevoltage-tunable capacitor 1206 is supplied a DC voltage as shown in FIG.12 which causes a change in the capacitance of the voltage-tunablecapacitor 1206 and thus enables one to the control of the directions ofthe maximum radiation beams and the minimum radiation beams (nulls) of aradio signal emitted from the array antenna 1102. A more detaileddiscussion about the components and advantages of the voltage-tunablecapacitor 1206 are provided below with respect to FIGS. 15A and 15B.

[0104] Referring to FIGS. 15A and 15B, there are respectively shown atop view and a cross-sectional side view of an exemplary voltage-tunablecapacitor 1206. The voltage-tunable capacitor 1206 includes a tunableferroelectric layer 1502 and a pair of metal electrodes 1504 and 1506positioned on top of the ferroelectric layer 1502. As shown in FIG. 14,one metal electrode 1504 is attached to one end of the parasitic antennaelement 1204. And, the other metal electrode 1504 is attached to thegrounding plate 1210. The controller 1208 applies the DC voltage to bothof the metal electrodes 1504 and 1506 (see FIG. 12). A substrate (notshown) may be positioned on the bottom of the ferroelectric layer 1502.The substrate may be any type of material that has a relatively lowpermittivity (e.g., less than about 30) such as MgO, Alumina, LaAlO3,Sapphire, or ceramic.

[0105] The tunable ferroelectric layer 1502 is a material that has apermittivity in a range from about 20 to about 2000, and has atunability in the range from about 10% to about 80% at a bias voltage ofabout 10 V/μm. In the preferred embodiment this layer is preferablycomprised of Barium-Strontium Titanate, BaxSr1-xTiO3 (BSTO), where x canrange from zero to one, or BSTO-composite ceramics. Examples of suchBSTO composites include, but are not limited to: BSTO—MgO, BSTO—MgAl2O4,BSTO—CaTiO3, BSTO—MgTiO3, BSTO—MgSrZrTiO6, and combinations thereof. Thetunable ferroelectric layer 1502 in one preferred embodiment has adielectric permittivity greater than 100 when subjected to typical DCbias voltages, for example, voltages ranging from about 5 volts to about300 volts. And, the thickness of the ferroelectric layer can range fromabout 0.1 μm to about 20 μm. Following is a list of some of the patentswhich discuss different aspects and capabilities of the tunableferroelectric layer 1502 all of which are incorporated herein byreference: U.S. Pat. Nos. 5,312,790; 5,427,988; 5,486,491; 5,635,434;5,830,591; 5,846,893; 5,766,697; 5,693,429 and 5,635,433.

[0106] The voltage-tunable capacitor 1206 has a gap 1508 formed betweenthe electrodes 1504 and 1506. The width of the gap 1508 is optimized toincrease ratio of the maximum capacitance Cmax to the minimumcapacitance Cmin (Cmax/Cmin) and to increase the quality factor (Q) ofthe device. The width of the gap 1508 has a strong influence on theCmax/Cmin parameters of the voltage-tunable capacitor 1206. The optimalwidth, g, is typically the width at which the voltage-tunable capacitor1206 has a maximum Cmax/Cmin and minimal loss tangent. In someapplications, the voltage-tunable capacitor 1206 may have a gap 1508 inthe range of 5-50 μm.

[0107] The thickness of the tunable ferroelectric layer 1502 also has astrong influence on the Cmax/Cmin parameters of the voltage-tunablecapacitor 1206. The desired thickness of the ferroelectric layer 1502 istypically the thickness at which the voltage-tunable capacitor 1206 hasa maximum Cmax/Cmin and minimal loss tangent. For example, an antennaarray 1102 a operating at frequencies ranging from about 1.0 GHz toabout 10 GHz, the loss tangent would range from about 0.0001 to about0.001. For an antenna array 1102 a operating at frequencies ranging fromabout 10 GHz to about 20 GHz, the loss tangent would range from about0.001 to about 0.01. And, for an antenna array 1102 a operatingfrequencies ranging from about 20 GHz to about 30 GHz, the loss tangentwould range from about 0.005 to about 0.02.

[0108] The length of the gap 1508 is another dimension that stronglyinfluences the design and functionality of the voltage-tunable capacitor1206. In other words, variations in the length of the gap 1508 have astrong effect on the capacitance of the voltage-tunable capacitor 1206.For a desired capacitance, the length can be determined experimentally,or through computer simulation.

[0109] The electrodes 1504 and 1506 may be fabricated in any geometry orshape containing a gap 1508 of predetermined width and length. In thepreferred embodiment, the electrode material is gold which is resistantto corrosion. However, other conductors such as copper, silver oraluminum, may also be used. Copper provides high conductivity, and wouldtypically be coated with gold for bonding or nickel for soldering.

[0110] Referring to FIGS. 16A and 16B, there are respectively shown twosimulation patterns one in a horizontal plane and the other in avertical plane that where obtained to indicate the performance of anexemplary array antenna 1102. The exemplary array antenna 1102 has aconfiguration similar to the array antenna 1102 a shown in FIG. 12 whereeach parasitic antenna element 1204 is arranged on a circumference of apredetermined circle around the radiating antenna element 1202. In thissimulation, the radiating antenna element 1202 and the parasitic antennaelements 1204 were separated from one another by 0.25λ0.

[0111] Referring again to FIG. 12, the antenna array 1102 a operates byexciting the radiating antenna element 1202 with the radio frequencyenergy of a radio signal. Thereafter, the radio frequency energy of theradio signal emitted from the radiating antenna element 1202 is receivedby the parasitic antenna elements 1204 which then re-radiate the radiofrequency energy after it has been reflected and phase changed by thevoltage-tunable capacitors 1206. The controller 1208 changes the phaseof the radio frequency energy at each parasitic antenna element 1204 byapplying a predetermined DC voltage to each voltage-tunable capacitor1206 which changes the capacitance of each voltage-tunable capacitor1206. This mutual coupling between the radiating antenna element 1202and the parasitic antenna elements 1204 enables one to steer theradiation beams and nulls of the radio signal that is emitted from theantenna array 1102 a.

[0112] Referring to FIG. 17, there is a perspective view thatillustrates the basic components of a second embodiment of the arrayantenna 1102 b. The array antenna 1102 b has a similar structure andfunctionality to array antenna 1102 a except that the antenna elements1702 and 1704 are configured as dipole elements instead of a monopoleelements as shown in FIG. 12. The array antenna 1102 b includes aradiating antenna element 1702 capable of transmitting and receivingradio signals and one or more parasitic antenna elements 1704 that areincapable of transmitting or receiving radio signals. Each parasiticantenna element 1704 (six shown) is located a predetermined distanceaway from the radiating antenna element 1702. A voltage-tunablecapacitor 1706 (six shown) is connected to each parasitic element 1704.A controller 1708 is used to apply a predetermined DC voltage to eachone of the voltage-tunable capacitors 1706 in order to change thecapacitance of each voltage-tunable capacitor 1706 and thus enable oneto control the directions of the maximum radiation beams and the minimumradiation beams (nulls) of a radio signal emitted from the array antenna1102 b. The controller 1708 may be part of or interface with the networkcontroller 1114 (see FIG. 11).

[0113] In the particular embodiment shown in FIG. 17, the array antenna1102 b includes one radiating antenna element 1702 and six parasiticantenna elements 1704 all of which are configured as dipole elements.The antenna elements 1702 and 1704 are electrically insulated from agrounding plate 1710. The grounding plate 1710 has an area large enoughto accommodate all of the antenna elements 1702 and 1704. In thepreferred embodiment, each parasitic antenna element 1704 is located ona circumference of a predetermined circle around the radiating antennaelement 1702. For example, the radiating antenna element 1702 and theparasitic antenna elements 1704 can be separated from one another byabout 0.2λ0-0.5λ0 where λ0 is the working free space wavelength of theradio signal.

[0114] Referring to FIG. 18, there is a perspective view thatillustrates the basic components of a third embodiment of the arrayantenna 1102 c. The array antenna 1102 c includes a radiating antennaelement 1002 capable of transmitting and receiving dual band radiosignals. The array antenna 1102 c also includes one or more lowfrequency parasitic antenna elements 1804 a (six shown) and one or morehigh frequency parasitic antenna elements 1804 b (six shown). Theparasitic antenna elements 1804 a and 1804 b are incapable oftransmitting or receiving radio signals. Each of the parasitic antennaelements 1804 a and 1804 b are locate a predetermined distance away fromthe radiating antenna element 1802. As shown, the low frequencyparasitic antenna elements 1804 a are located on a circumference of a“large” circle around both the radiating antenna element 1802 and thehigh frequency parasitic antenna elements 1804 b. And, the highfrequency parasitic antenna elements 1804 b are located on acircumference of a “small” circle around the radiating antenna element1802. In this embodiment, the low frequency parasitic antenna elements1804 a are the same height as the radiating antenna element 1802. And,the high frequency parasitic antenna elements 1804 b are shorter thanthe low frequency parasitic antenna elements 1804 a and the radiatingantenna element 1802.

[0115] The array antenna 1102 c also includes one or more low frequencyvoltage-tunable capacitors 1806 a (six shown) which are connected toeach of the low frequency parasitic elements 1804 a. In addition, thearray antenna 1102 c includes one or more high frequency voltage-tunablecapacitors 1806 b (six shown) which are connected to each of the highfrequency parasitic elements 1804 b. A controller 1008 is used to applya predetermined DC voltage to each one of the voltage-tunable capacitors1806 a and 1806 b in order to change the capacitance of eachvoltage-tunable capacitor 1806 a and 1806 b and thus enable one tocontrol the directions of the maximum radiation beams and the minimumradiation beams (nulls) of a dual band radio signal that is emitted fromthe array antenna 1102 c. The controller 1808 may be part of orinterface with the network controller 1114 (see FIG. 11).

[0116] In the particular embodiment shown in FIG. 18, the array antenna1102 c includes one radiating antenna element 1802 and twelve parasiticantenna elements 1804 a and 1804 b all of which are configured asmonopole elements. The antenna elements 1802, 1804 a and 1804 b areelectrically insulated from a grounding plate 1810. The grounding plate1810 has an area large enough to accommodate all of the antenna elements1802, 1804 a and 1804 b. It should be understood that the low frequencyparasitic antenna elements 1804 a do not affect the high frequencyparasitic antenna elements 1804 b and vice versa.

[0117] The antenna array 1102 c operates by exciting the radiatingantenna element 1802 with the high and low radio frequency energy of adual band radio signal. Thereafter, the low frequency radio energy ofthe dual band radio signal emitted from the radiating antenna element1802 is received by the low frequency parasitic antenna elements 1804 awhich then re-radiate the low frequency radio frequency energy after ithas been reflected and phase changed by the low frequencyvoltage-tunable capacitors 1806 a. Likewise, the high frequency radioenergy of the dual band radio signal emitted from the radiating antennaelement 1802 is received by the high frequency parasitic antennaelements 1804 b which then re-radiate the high frequency radio frequencyenergy after it has been reflected and phase changed by the highfrequency voltage-tunable capacitors 1806 b. The controller 1808 changesthe phase of the radio frequency energy at each parasitic antennaelement 1804 a and 1804 b by applying a predetermined DC voltage to eachvoltage-tunable capacitor 1806 a and 1806 b which changes thecapacitance of each voltage-tunable capacitor 1806 a and 1806 b. Thismutual coupling between the radiating antenna element 1802 and theparasitic antenna elements 1804 a and 1804 b enables one to steer theradiation beams and nulls of the dual band radio signal that is emittedfrom the antenna array 1102 c. The array antenna 1102 c configured asdescribed above can be called a dual band, endfire, phased array antenna1102 c.

[0118] Although the array antennas described above have radiatingantenna elements and parasitic antenna elements that are configured aseither a monopole element or dipole element, it should be understoodthat these antenna elements can have different configurations. Forinstance, these antenna elements can be a planar microstrip antenna, apatch antenna, a ring antenna or a helix antenna.

[0119] In the above description, it should be understood that thefeatures of the array antennas apply whether it is used for transmittingor receiving. For a passive array antenna the properties are the samefor both the receive and transmit modes. Therefore, no confusion shouldresult from a description that is made in terms of one or the other modeof operation and it is well understood by those skilled in the art thatthe invention is not limited to one or the other mode.

[0120] Following are some of the different advantages and features ofthe array antenna 1102 of the present invention:

[0121] The array antenna 1102 has a simple configuration.

[0122] The array antenna 1102 is relatively inexpensive.

[0123] The array antenna 1102 has a high RF power handling parameter ofup to 20 W. In contrast, the traditional array antenna 200 has a RFpower handling parameter that is less than 1 W.

[0124] The array antenna 1102 has a low linearity distortion representedby IP3 of upto +65 dBm. In contrast, the traditional array antenna 200has a linearity distortion represented by IP3 of about +30 dBm.

[0125] The array antenna 1102 has a low voltage-tunable capacitor loss.

[0126] The dual band array antenna 1102 c has two bands each of whichworks upto 20% of frequency. In particular, there are two centerfrequency points for the dual band antenna f0 each of which has abandwidth of about 10% ˜20% [(f1+f2)/2=f0, Bandwidth=(f2−f1)/f0* 100%]where f1 and f2 are the start and end frequency points for one frequencyband. Whereas the single band antenna 1102 a and 302 b works in the f1,to f2 frequency range. The dual band antenna 1102 c works in one f1 tof2 frequency range and another f1 to f2 frequency range. The two centerfrequency points are apart from each other, such as more than 10%. Forexample, 1.6 GHz˜1.7 GHz and 2.4 GHz˜2.5 GHz, etc. The traditional arrayantenna 200 cannot support a dual band radio signal.

[0127] As mentioned above and described in more detail below, theantennas of the present invention can have switchable polarizations toimprove performance. As shown in FIG. 19 generally as 1900, the antenna1905 provides two RF signals 1930 and 1935, one with Verticalpolarization 1930 and one with Horizontal polarization 1935. Each RFsignal will then pass through a single pole double throw switch.Vertically polarized signal 1930 will pass through single pole doublethrow switch SW1, 1905, and horizontally polarized signal 1935 will passthrough single pole double throw switch SW2, 1925.

[0128] For both single pole double throw switches SW1, 1905, and SW2,1925, one position of the switches outputs the signal unchanged, i.e.,with the same polarization, and the other position will pass the signalthrough the hybrid coupler 1910. The function of hybrid coupler 1910 isto convert vertical/horizontal polarizations into two slantpolarizations at +45° and −45° as shown at 1940.

[0129] Switches SW3, 1915, and SW4, 1920, select the desired set ofpolarizations, namely Vertical/Horizontal or +45° and −45° slant. Thispolarization diversity provided by antenna 1905 will greatly enhance theperformance of the present RFID system, especially in presence ofmulti-path fading.

[0130] Not meant to be exhaustive or exclusive, the following tableshows some of the specific different frequency bands used in thisembodiment of the present invention. Frequency band Applications 868-870MHz. SRD (Short Range Devices, RFID) in CEPT countries Most devices use869 MHz for RFID up to 500 mW 902-928 MHz ISM and RFID applications inRegion 2 covers North America, most devices use 915 MHz for RFID 4W inNorth America/Canada 918-926 MHz RFID in Australia. Most devices use 923MHz 950-956 MHz RFID in Japan, just allocated

[0131] With any of the aforementioned embodiments, because of the uniquecapabilities of the RF ID tag readers and RF ID tags with the novelscanning, stearable and array antennas provided herein, positioninformation can be readily obtained. This is accomplished with thepresent invention by associating at least one RF ID tag with anythingwhere position information or tracking information is desired from, suchas any object, person or thing. Then communication is establishedbetween at least one RF ID tag reader and said at least one RF ID tag.In a first embodiment, at least one RF ID tag reader includes at leasttwo electronically steerable scanning antennas.

[0132] At this point one can determine the location of said at least oneRF ID tag relative to said at least one RF ID tag reader bytriangulating the angular information between said at least one RF IDtag and said at least two electronically steerable scanning antennasassociated with said at least one RF ID tag reader.

[0133] Improved accuracy of the position information can be obtained bydetermining the signal strength of the communication between said atleast one RF ID tag and said at least one RF ID tag reader. Also,improved accuracy is provided by determining the time of flight of RFsignals between said at least one RF ID tag and said at least one RF IDtag reader to improve accuracy of said position information.

[0134] In a second embodiment multiple RF tag readers are used insteadof multiple antennas with at least one RF ID tag reader. Hence, theposition of an object, person or thing, is determined by associating atleast one RF ID tag with said object, person or thing and establishingcommunication between at least two RF ID tag readers and said at leastone RF ID tag, said at least two RF ID tag readers including at leastone electronically steerable scanning antenna. Then the location of saidat least one RF ID tag relative to said at least two RF ID tag readersis determined by triangulating the angular information between said atleast one RF ID tag and said at least two RF ID tag reader using said atleast one electronically steerable scanning antennas.

[0135] As above, the accuracy can be improved by determining the signalstrength of the communication between said at least one RF ID tag andsaid at least two RF ID tag readers and/or by determining the time offlight of RF signals between said at least one RF ID tag and said atleast two RF ID tag readers to improve accuracy of said positioninformation.

[0136] The aforementioned method of determining the position of anobject, person or thing is accomplished by the following system, whereinat least one RF ID tag is associated with said object, person or thingand at least one RF ID tag reader establishes communication with said atleast one RF ID tag. The at least one RF ID tag reader includes at leasttwo electronically steerable scanning antennas and determines therelative location of said at least one RF ID tag by triangulating theangular information between said at least one RF ID tag and said atleast two electronically steerable scanning antennas which areassociated with said at least one RF ID tag reader.

[0137] Again, the accuracy can be improved by including in the system ameans for determining the signal strength of the communication betweensaid at least one RF ID tag and said at least one RF ID tag reader.There are a number of methods known to enable this signal strengthdetermination and well known to those of ordinary skill in the art andthus is not elaborated on herein.

[0138] Further, the accuracy can be improved by providing a means fordetermining the time of flight of RF signals between said at least oneRF ID tag and said at least one RF ID tag reader.

[0139] The system can include multiple antennas with at least one RF IDcard reader as above or can include multiple RF ID tag readersassociated with at least one electronically steerable scanning antennaas set forth below, wherein the object, person or thing positiondetermination system comprises at least one RF ID tag associated withsaid object, person or thing and in the embodiment at least two RF IDtag readers which establish communication with said at least one RF IDtag. The at least two RF ID tag readers include at least oneelectronically steerable scanning antenna.

[0140] The at least two RF ID tag readers determine the relativelocation of said at least one RF ID tag by triangulating the angularinformation between said at least one RF ID tag and said at least oneelectronically steerable scanning antennas associated with said at leasttwo RF ID tag readers.

[0141] With the at least two RF ID tag reader embodiment, accuracy canbe improved by providing a means for determining the signal strength ofthe communication between said at least one RF ID tag and said at leasttwo RF ID tag readers to improve accuracy of said position information.It can be further improved by providing a means for determining the timeof flight of RF signals between said at least one RF ID tag and said atleast two RF ID tag readers to improve accuracy of said positioninformation.

[0142] While the present invention has been described in terms of whatare at present believed to be its preferred embodiments, those skilledin the art will recognize that various modifications to the discloseembodiments can be made without departing from the scope of theinvention as defined by the following claims. Further, although aspecific scanning antenna utilizing dielectric material is beingdescribed in the preferred embodiment, it is understood that anyscanning antenna can be used with any type of reader any type of tag andnot fall outside of the scope of the present invention.

What is claimed is:
 1. An RF ID card reader, comprising: RF ID circuitryto generate an RF ID signal; a transceiver in communication with said RFID circuitry; and a scanning antenna associated with said transceiverfor scanning an area for at least one tag and establishing communicationwith at least one tag.
 2. The RF ID card reader of claim 1, wherein saidscanning antenna comprises: at least one RF module, said at least one RFmodule further comprising at least one RF connection for receipt of atleast one RF signal and at least one tunable or switchable device; a RFmotherboard for acceptance of RF signals and distribution of thetransmit energy to said RF module at the appropriate phases to generatea beam in the commanded direction and width; and a controller fordetermining the correct signal to send to said at least one RF module.3. The RF ID card reader of claim 2, wherein said at least one RF signalhas either single or dual polarization which can be either linear orcircular.
 4. The RF ID card reader of claim 2, wherein said at least oneRF module is nine RF modules.
 5. The RF ID card reader of claim 1,wherein an interface connects said scanning antenna with amicrocontroller associated with said reader.
 6. The RF ID card reader ofclaim 2, wherein said beam width and steer have at least a 6 dBi gainthroughout a 360 degree azimuth scan or any segmentation of 360 degrees.7. The RF ID card reader of claim 2, further comprising a Radomesurrounding said at least one RF module and said RF mother board.
 8. TheRF ID card reader of claim 2, further comprising a base attached to saidradome housing said controller, said base provides openings forreception of an RF connector, power supply and data input.
 9. The RF IDcard reader of claim 2, wherein said scanning antenna operation is inany one, all or part of the following frequencies: the 2.4 GHz band; the5.1 to 5.8 GHz band; the 860-960 MHz band; or the 433 MHz band.
 10. TheRF ID card reader of claim 2, further comprising a software driver tocontrol said scanning antenna azimuth scan angle to maximize a receivedwireless signal.
 12. The RF ID card reader of claim 2, furthercomprising a three way divider, the output of said power dividerconnects to a phase shifter module.
 13. An RF ID tag system, comprising:at least one RF ID tag; at least one RF ID tag reader, said at least onetag reader including at least one RF ID tag reader microcontroller; andat least one transceiver associated with said at least onemicrocontroller, said at least one transceiver in communication with atleast one scanning antenna for transmitting signals to and receivingsignals from said at least one tag.
 14. The RF ID tag system of claim13, wherein said at least one scanning antenna comprises: at least oneRF module, said at least one RF module further comprising at least oneRF connection for receipt of at least one RF signal and at least ontunable or switchable device; an RF motherboard for acceptance of RFsignals and distribution of the transmit energy to said RF module at theappropriate phases to generate a beam in the commanded direction andwidth; and a controller for determining the correct signal to send tosaid at least one RF module.
 15. The RF ID card reader of claim 14,wherein said at least one RF signal has either single or dualpolarization which can be either linear or circular.
 16. The RF ID cardreader of claim 14, wherein said at least one RF module is nine RFmodules.
 17. The RF ID card reader of claim 13, wherein an interfaceconnects said scanning antenna with a microcontroller associated withsaid reader.
 18. The RF ID card reader of claim 14, wherein said beamwidth and steer have at least a 6 dBi gain throughout a 360 degreeazimuth scan or any segmentation of 360 with at least 6 dBi gain. 19.The RF ID card reader of claim 14, further comprising a Radomesurrounding said at least one RF module and said RF mother board. 20.The RF ID card reader of claim 14, further comprising a base attached tosaid radome housing said controller, said base provides openings forreception of an RF connector, power supply and data input.
 21. The RF IDcard reader of claim 14, wherein said scanning antenna operation is inany one, all or part of the following frequencies: the 2.4 GHz band; the5.1 to 5.8 GHz band; the 860-960 MHz band; or the 433 MHz band.
 22. TheRF ID card reader of claim 14, further comprising a software driver tocontrol the said scanning antenna azimuth scan angle to maximize areceived wireless signal.
 23. The RF ID card reader of claim 2, furthercomprising a three way divider, the output of said power dividerconnects to a phase shifter module.
 24. A method of tracking an object,person or thing, comprising the steps of: associating an RF ID tag withsaid object, person or thing; providing an RF ID tag reader with ascanning antenna for transmitting information to, and receivinginformation from, said RF ID tag, said RF ID tag containing informationabout said object, person or thing.
 25. The method of tracking anobject, person or thing of claim 24, wherein said scanning antennacomprises: at least one RF module, said at least one RF module furthercomprising at least one RF connection for receipt of at least one RFsignal and at least one tunable or switchable device. an RF motherboardfor acceptance of RF signals and distribution of the transmit energy tosaid RF module at the appropriate phases to generate a beam in thecommanded direction and width; and a controller for determining thecorrect signal to send to said at least one RF module.
 26. The method oftracking an object, person or thing of claim 25, wherein said at leastone RF signal is at least two RF signal has either single or dualpolarization which can be either linear or circular.
 27. The method oftracking an object, person or thing of claim 25, wherein said at leastone RF module is nine RF modules.
 28. The method of tracking an object,person or thing of claim 24, wherein an interface connects said scanningantenna with a microcontroller associated with said reader.
 29. Themethod of tracking an object, person or thing of claim 25, wherein saidbeam width and steer have at least a 6 dBi gain throughout a 360 degreeazimuth scan or any segmentation of 360 degrees with at least 6 dBigain.
 30. The method of tracking an object, person or thing of claim 25,wherein said scanning further comprises a Radome surrounding said atleast one RF module and said RF mother board.
 31. The method of trackingan object, person or thing of claim 25, wherein said scanning antennafurther comprises a base attached to said radome housing saidcontroller, said base provides openings for reception of an RFconnector, power supply and data input.
 32. The method of tracking anobject, person or thing of claim 25, wherein said scanning antennaoperation is in any one, all or part of the following frequencies: the2.4 GHz band; the 5.1 to 5.8 GHz band; the 860-960 MHz band; or the 433MHz band.
 33. The method of tracking an object, person or thing of claim25, wherein said scanning antenna further comprises a software driver tocontrol said scanning antenna azimuth scan angle to maximize a receivedwireless signal.
 34. The method of tracking an object, person or thingof claim 25, wherein said scanning antenna further comprises a three waydivider, the output of said power divider connects to a phase shiftermodule.
 35. An RF ID card reader, comprising: RF ID circuitry togenerate an RF ID signal; a transceiver in communication with said RF IDcircuitry; and an array antenna associated with said transceiver forscanning an area for at least one tag and establishing communicationwith at least one tag.
 36. The RF ID card reader of claim 35, whereinsaid array antenna comprises: a radiating antenna element; at least oneparasitic antenna element; at least one voltage-tunable capacitorconnected to said at least one parasitic antenna element; and acontroller for applying a voltage to each voltage-tunable capacitor tochange the capacitance of each voltage-tunable capacitor and thuscontrol the directions of maximum radiation beams and minimum radiationbeams of a radio signal emitted from said radiating antenna element andsaid at least one parasitic antenna element.
 37. The RF ID card readerof claim 36, wherein each voltage-tunable capacitor includes a tunableferroelectric layer and a pair of metal electrodes separated by apredetermined distance and located on top of the ferroelectric layer.38. The RF ID card reader of claim 36, wherein each parasitic antennaelement is arranged a predetermined distance from said radiating antennaelement.
 39. The RF ID card reader of claim 36, wherein said radiatingantenna element and said at least one parasitic antenna element areseparated from one another by about 0.2λ0-0.5λ0 where λ0 is a workingfree space wavelength of the radio signal.
 40. The RF ID card reader ofclaim 36, wherein said radiating antenna element and said at least oneparasitic antenna element each have one of the following configurations:a monopole antenna; a dipole antenna; a planar microstrip antenna; apatch antenna; a ring antenna; or a helix antenna.
 41. The RF ID cardreader of claim 36, wherein said minimum radiation beams are nulls andsaid maximum radiation beams are 360 degree steerable radiation beams.42. The RF ID card reader of claim 36, wherein: said radiating antennaelement is a dual band radiating antenna element; and said at least oneparasitic antenna element includes at least one low frequency parasiticantenna element and at least one high frequency parasitic antenna. 43.The RF ID card reader of claim 35, wherein said array antenna comprises:a radiating antenna element excited by radio frequency energy of a radiosignal; at least one parasitic antenna element; at least onevoltage-tunable capacitor connected to said at least one parasiticantenna element; each parasitic antenna element receives the radiofrequency energy of the radio signal emitted from said radiating antennaelement and then re-radiates the radio frequency energy of the radiosignal after the radio frequency energy has been reflected and phasechanged by each voltage-tunable capacitor; and a controller that phasechanges the radio frequency energy at each parasitic antenna element byapplying a voltage to each voltage-tunable capacitor to change thecapacitance of each voltage-tunable capacitor and thus enables thesteering of the radiation beams and nulls of the radio signal emittedfrom said radiating antenna element and said at least one parasiticantenna element.
 44. The RF ID card reader of claim 43, wherein eachvoltage-tunable capacitor includes a tunable ferroelectric layer and apair of metal electrodes separated by a predetermined distance andlocated on top of the ferroelectric layer.
 45. The array antenna ofclaim 43, wherein said at least one parasitic antenna element isarranged on a circumference of a predetermined circle around saidradiating antenna element.
 46. The array antenna of claim 43, whereinsaid radiating antenna element and said at least one parasitic antennaelement are separated from one another by about 0.2λ0-0.5λ0 where λ0 isa working free space wavelength of the radio signal.
 47. The arrayantenna of claim 43, wherein said radiating antenna element and said atleast one parasitic antenna element each have one of the followingconfigurations: a monopole antenna; a dipole antenna; a planarmicrostrip antenna; a patch antenna; a ring antenna; or a helix antenna.48. The array antenna of claim 43, wherein: said radiating antennaelement is a dual band radiating antenna element; and said at least oneparasitic antenna element includes at least one low frequency parasiticantenna element and at least one high frequency parasitic antenna. 49.An RF ID card reader, comprising: RF ID circuitry to generate an RF IDsignal; a transceiver in communication with said RF ID circuitry; and aswitched polarization antenna associated with said transceiver forcommunication with at least one tag.
 50. The RF ID card reader of claim49, wherein said switched polarization antenna is a switchedpolarization scanning antenna for scanning an area for at least one tagand establishing communication with at least one tag.
 51. The RF ID cardreader of claim 49, wherein said polarization antenna provides aplurality of RF signals, at least one RF signal with Verticalpolarization and at least one RF signal with Horizontal polarization.52. The RF ID card reader of claim 49, wherein said at least one RFsignal with horizontal polarization and at least one RF signal withvertical polarization will pass through at least one single pole doublethrow switch, said at least one single pole double throw switch capableof outputting said at least one RF signal with horizontal polarizationand at least one RF signal with vertical polarization to a hybridcoupler, or which passes said at least one RF signal with horizontalpolarization and at least one RF signal with vertical polarization withthe same polarization.
 53. The RF ID card reader of claim 50, whereinsaid hybrid coupler converts vertical/horizontal polarizations into twoslant polarizations at +45° and −45°.
 54. The RF ID card reader of claim50, further comprising at least one switch for receiving at least one RFsignal from said at least one RF signal with horizontal polarization andat least one RF signal with vertical polarization, said at least oneswitch selecting the desired set of polarizations, namelyVertical/Horizontal or +45° and −45° slant.
 55. A method of tracking anobject, person or thing, comprising the steps of: associating an RF IDtag with said object, person or thing; providing an RF ID tag readerwith a switched polarization antenna for transmitting information to,and receiving information from, said RF ID tag, said RF ID tagcontaining information about said object, person or thing.
 56. Themethod of tracking an object, person or thing of claim 55, wherein saidswitched polarization antenna is a switched polarization scanningantenna for scanning an area for at least one tag and establishingcommunication with at least one tag.
 57. The method of tracking anobject, person or thing of claim 55, wherein said polarization antennaprovides a plurality of RF signals, at least one RF signal with Verticalpolarization and at least one RF signal with Horizontal polarization.58. The method of tracking an object, person or thing of claim 55,wherein said at least one RF signal with horizontal polarization and atleast one RF signal with vertical polarization will pass through atleast one single pole double throw switch, said at least one single poledouble throw switch capable of outputting said at least one RF signalwith horizontal polarization and at least one RF signal with verticalpolarization to a hybrid coupler, or which passes said at least one RFsignal with horizontal polarization and at least one RF signal withvertical polarization with the same polarization.
 59. The method oftracking an object, person or thing of claim 55, wherein said hybridcoupler converts vertical/horizontal polarizations into two slantpolarizations at +45° and −45°.
 60. The method of tracking an object,person or thing of claim 55, further comprising at least one switch forreceiving at least one RF signal from said at least one RF signal withhorizontal polarization and at least one RF signal with verticalpolarization, said at least one switch selecting the desired set ofpolarizations, namely Vertical/Horizontal or +45 ° and −45° slant. 61.An RF ID tag system, comprising: at least one RF ID tag; at least one RFID tag reader, said at least one tag reader including at least one RF IDtag reader microcontroller; and at least one transceiver associated withsaid at least one microcontroller, said at least one transceiver incommunication with at least one switched polarization antenna fortransmitting signals to and receiving signals from said at least onetag.
 62. The RF ID tag system of claim 61, wherein said switchedpolarization antenna is a switched polarization scanning antenna forscanning an area for at least one tag and establishing communicationwith at least one tag.
 63. The RF ID tag system of claim 61, whereinsaid switched polarization antenna provides a plurality of RF signals,at least one RF signal with Vertical polarization and at least one RFsignal with Horizontal polarization.
 64. The RF ID tag system of claim61, wherein said at least one RF signal with horizontal polarization andat least one RF signal with vertical polarization will pass through atleast one single pole double throw switch, said at least one single poledouble throw switch capable of outputting said at least one RF signalwith horizontal polarization and at least one RF signal with verticalpolarization to a hybrid coupler, or which passes said at least one RFsignal with horizontal polarization and at least one RF signal withvertical polarization with the same polarization.
 65. The RF ID tagsystem of claim 61, wherein said hybrid coupler convertsvertical/horizontal polarizations into two slant polarizations at +45°and −45°.
 66. The RF ID tag system of claim 61, further comprising atleast one switch for receiving at least one RF signal from said at leastone RF signal with horizontal polarization and at least one RF signalwith vertical polarization, said at least one switch selecting thedesired set of polarizations, namely Vertical/Horizontal or +45° and−45° slant.
 67. A method of locating the position of an object, personor thing, comprising the steps of: associating at least one RF ID tagwith said object, person or thing; establishing communication between atleast one RF ID tag reader and said at least one RF ID tag, said atleast one RF ID tag reader including at least two electronicallysteerable scanning antennas; and determining the location of said atleast one RF ID tag relative to said at least one RF ID tag reader bytriangulating the angular information between said at least one RF IDtag and said at least two electronically steerable scanning antennasassociated with said at least one RF ID tag reader.
 68. The method oflocating the position of an object, person or thing of claim 67, furthercomprising determining the signal strength of the communication betweensaid at least one RF ID tag and said at least one RF ID tag reader toimprove accuracy of said position information.
 69. The method oflocating the position of an object, person or thing of claim 67, furthercomprising determining the time of flight of RF signals between said atleast one RF ID tag and said at least one RF ID tag reader to improveaccuracy of said position information.
 70. A method of locating theposition of an object, person or thing, comprising the steps of:associating at least one RF ID tag with said object, person or thing;establishing communication between at least two RF ID tag readers andsaid at least one RF ID tag, said at least two RF ID tag readersincluding at least one electronically steerable scanning antenna; anddetermining the location of said at least one RF ID tag relative to saidat least two RF ID tag readers by triangulating the angular informationbetween said at least one RF ID tag and said at least two RF ID tagreader using said at least one electronically steerable scanningantennas.
 71. The method of locating the position of an object, personor thing of claim 70, further comprising determining the signal strengthof the communication between said at least one RF ID tag and said atleast two RF ID tag readers to improve accuracy of said positioninformation.
 72. The method of locating the position of an object,person or thing of claim 70, further comprising determining the time offlight of RF signals between said at least one RF ID tag and said atleast two RF ID tag readers to improve accuracy of said positioninformation.
 73. An object, person or thing position determinationsystem, comprising: at least one RF ID tag associated with said object,person or thing; at least one RF ID tag reader, said at least one RF IDtag reader establishing communication with said at least one RF ID tag;said at least one RF ID tag reader including at least two electronicallysteerable scanning antennas; and said at least one RF ID tag readerdetermining the relative location of said at least one RF ID tag bytriangulating the angular information between said at least one RF IDtag and said at least two electronically steerable scanning antennasassociated with said at least one RF ID tag reader.
 74. The object,person or thing position determination system of claim 73, furthercomprising a means for determining the signal strength of thecommunication between said at least one RF ID tag and said at least oneRF ID tag reader to improve accuracy of said position information. 75.The object, person or thing position determination system of claim 73,further comprising a means for determining the time of flight of RFsignals between said at least one RF ID tag and said at least one RF IDtag reader to improve accuracy of said position information.
 76. Anobject, person or thing position determination system, comprising: atleast one RF ID tag associated with said object, person or thing; atleast two RF ID tag readers, said at least two RF ID tag readersestablishing communication with said at least one RF ID tag; said atleast two RF ID tag readers including at least one electronicallysteerable scanning antenna; and said at least two RF ID tag readersdetermining the relative location of said at least one RF ID tag bytriangulating the angular information between said at least one RF IDtag and said at least one electronically steerable scanning antennasassociated with said at least two RF ID tag readers.
 77. The object,person or thing position determination system of claim 76, furthercomprising a means for determining the signal strength of thecommunication between said at least one RF ID tag and said at least twoRF ID tag readers to improve accuracy of said position information. 75.The object, person or thing position determination system of claim 76,further comprising a means for determining the time of flight of RFsignals between said at least one RF ID tag and said at least two RF IDtag readers to improve accuracy of said position information.